You may have read about “secret tunnels” under Whitehall, and indeed there are some – but here is a tale of one that is not exactly a secret – more just forgotten.

The Waterloo and Whitehall Pneumatic Railway was a air piston based railway service which was expected to link Great Scotland Yard at Whitehall with Waterloo on the southern side of the river.

It was a piston based railway, leading on from earlier works with hydraulic parcel chutes in the City, and a test passenger train platform built at Crystal Palace.

Construction of the scheme began around 1865, but ceased in 1868 following a banking crisis which resulted in one of the main financial backers going bust.

Exact details of what was built seem confused â€“ but it now seems that the tunnel from Great Scotland Yard to the river was actually built.

The river was also dredged at that point, and possibly brick foundations might have been laid along part of the under-river route.

There is an lithograph I found on the rather excellent british-history website which shows the Embankment cross section at what looks like Charring Cross showing off the Bazalgette sewer system and District train lines â€“ with the Pneumatic Railway in place â€“ but judging by the records, I can only presume that this is a projected side-view of an expected future, as the picture shows the tunnel going under the river itself, and I can’t find any record of that bit actually being built.

However, studying the picture shows that there is indeed the early Hungerford Bridge and Charring Cross station, leaving me in no question that the deeper tunnel is the expected pneumatic railway as discussed above.

The tunnel itself would have been a brick-lined pipeline of diameter 18 (or in some records, 13) feet, and the air pumping station would have been at Waterloo.

Now, here is the question â€“ how much of that quite deep tunnel still exists, and can we get into it

I am quite interested in this, and will be doing more hunting in the archives to see if I can find some maps and more exact information. The thing with the Victorians is that they were incredibly detailed record keepers, so if you find the files, then the detail is considerable. Alas, most of the records are often lost, and then you can hit a bit of a black hole.

As an aside, the Tower Subway tunnel (and which I can’t get into – sobs) which was built a few years later had also considered using pneumatics, but later settled on a chain to pull carriages along the tunnel length. This was removed only a couple of years later and the tunnel converted into pedestrian use.